Smooth-textured lithium-base greases



Patented Jan. 1, 1952 SMOOTH-TEXTURED LITHIUM-BASE GREASES Paul R. McCarthy, Allison ark, .Pa., assignor to Gulf Research & Development, Company, Pittsburgh, Pa., a. corporation of Delaware No Drawing. Application April 24, 1950, Serial No. 157,845

This invention relates to improved grease compositions and more particularly to smooth-textured lithium-base greases.

The addition of a lithium compound such as the lithium soap of a higher fatty acid, such as lithium stearate, lithium palmitate, lithium oleate, and the like, and the lithium salts of other organic acids, such as acetic, butyric, ethyl butyric', ethyl hexoic, and caproic acid to a mineral oil produces grease compositions having properties that are not only widely different from the other alkali metal soap-type greases but also they are chemically and physically more stable to temperature. However, greases prepared from viscous mineral oils such as those having a viscosity above about 750 SUS at 100 F. and a lithium compound of the above type, have not been entirely satisfactory in that the greases prepared from these more viscous oils have had a grainy texture.

It is therefore an object achieved by this invention to provide smooth-textured lithium-base greases prepared from oils having a viscosity above about 750 SUS at 100 F. A further object achieved by this invention is to provide smoothtextured lithium-base greases having improved worked and unworked penetration characteristics.

These and other objects achieved by this invention will become apparent from the following detailed discussion.

V I have discovered that grease compositions having a smooth texture and improved' penetra tion characteristics can be made from high viscosity mineral oils and a lithium soap by compounding therewith a small amount of a. hydrogenated rosin. This discovery is surprising, particularly in view of the fact that the addition of a small amount of a hydrogenated rosin toa lithium base grease prepared from a mineral 'oilhaving' a viscosity below about 750 SUS at 100 F.

is detrimental to the penetration characteristics- That a hydrogenated rosin will of the grease. improve the consistency of a lithium-base grease by decreasing its. penetration characteristics is further surprising in that the addition of a natural or unhydrogenated rosin such as Wood rosin rosin is obtained by the addition of hydrogen to' the double bonds of abietic acid. The amount of 10 Claims. (01. 25242) 4000 SUS at 100 F. may be secured. The oil content of the greases prepared according to this invention comprises about 84 to about 95 per cent by weight of the grease composition. The particular oil as well as the optimum amount of oil employed depends upon the characteristics desired in the final composition.

The lithium soap employed in the present in{ ium soaps of either substantially pure fatty acids or mixtures of fatty acids such as those obtained from the variousfatty oils, such as cottonseed oil, rapeseed oil, animal oils, fish oils, and the like. The'saturated fatty acids such as those derived from hydrogenated oils of vegetable, animal; and marine extraction may also be used."

For example, I may prepare the lithium soap of the fatty acids obtained by the hydrogenation of a fish oil, such as sardine oil, herring oil, cod oil, menhaden oil, and the like. The hydrogenation of these oils is not a part of this invention but may be carried out by various known processes such, for example, as the process described on pages 3'72 to 430 of Hydrogenation of Organic Substances, third edition, by Carlton Ellis, D. .Van' Nostrand Co.,' Inc., New York (1930). The amount of the lithium compound employed should be sufllcient to thicken the oil to the consistency of a grease. For greases of the type employed in the lubrication of automobile chassis and wheel bearings, the lithium soap content of the'grease comprises about 5 to about 15 per cent' by weight of the grease composition.

.Rosin, sometimes called colophony, is the residue obtained on distilling turpentine from hard pine resin. constituent of rosin and is obtained fromthe lat.- ter by distillation. Abietic acid is a carboxylic acidcontaining two double bonds. Hydrogenated hydrogen added may be sufficient to saturate the two unsaturated bonds of abietic acid or it may be any amount to produce substantial partial hydrogenation. The hydrogenated rosins which I use are the rosins of at least, about 40 per cent saturation toand including fullyhydrogenated';

rosin. A particularly useful hydrogenated rosin for the purposes of my invention is one which has been hydrogenated to about per cent of Abietic acid, C20H3002, is the chief 3 capacity and has a melting point of about 168 F. The quantity of the hydrogenated rosin employed constitutes from about 0.2 to about 1.5 per cent by weight of the totalgrease composition, the

higher amount generally being used when making greases from oils having viscosities of 3000 to 4000 SUS at 100 F. In general, improved penetration characteristics are obtained when the weight ratio of the hydrogenated rosin to the lithium soap is between about 1:4 and 1:30. In some instances improvement is obtained with ratios as high as 1:50. However, for optimum improvement the ratio of hydrogenated rosin to lithium soap to be employed in any particular case depends upon the'characteristics of the oil used and e the characteristics desired in the final grease I have found that the weight ratio of hydrogen ated rosin to lithium soap for optimum improvement in chassis lubricants is maintained between about 1:5 and about 1:10. Naturally, these ratios will change when different types of lubricants are prepared. For instance, I have made excellent wheel bearing lubricants from oils'having viscosities of about 1000 SUS at 100 F. when employing the'hydrogenated rosin and lithium soap in weight ratios between about 1:6 and about 1:20. s

In instances where the grease compositions of my invention are subjected to prolonged use under oxidizing conditions, I advantageously incorporate in the. grease a-small amount of a diaryl amine oxidation inhibitor: As examples of some available lithium stearate, the oil and the lithium compound are added to a jacketed kettle equipped with a stirrer. The oil-stearate mixture is then stirred and heated to about 420 F. Thehydrogenated rosin is then added while the stirring and heating are continued. The grease is then cooled to about 200 to about 250 F. and pumped to homogenize. According to another embodiment, when the lithium compound is prepared in situ, about 30 per cent of the total oil, together with all of the acid, and lithium hydroxide in an amount sufiicient to react with the acid and to produce a composition which is approximately neutral, is placed in a pressure kettle. The contents of the kettle are then stirred and slowly heated to a temperature of about 320 F. under a pressure of about 80 to about 90 pounds per square inch until saponification is complete. The kettle contents are then transferred to anopen kettle where stirring is continued and the temperature raised to about 400 F. over a period of about one hour. This temperature is then maintained for an additional 30 minutes or until dehydration is substantially complete. The remainder of the oil and the hydrogenated rosin are then added and the mixture stirred and heated at about 100 F. for an additional l0 minutes. The grease composition thus formed is then cooled with stirring to about 200 to about 250 F. The cooled grease is then pumped to homogenize. If it is desired, an anti oxidant may be added to the grease composition during the cooling procedure.

When hydrogenated rosin is added to a lithium-base grease prepared from oils having viscosities at 100 F. of about 500 SUS or less, a softer grease is obtained, as evidenced by the data 7 for the consistency of the compositions given in Table 1.. The oil used in the compositions listed of the diaryl amines which may be used the compositions of my invention may be mentioned diphenylamine, phenyl alpha naphthylamine,

phenyl beta naphthylamine, alpha alpha-, alpha beta.-, and betav beta-dinaphthylamines, and the like. The amount of the diaryl amine employed will depend to a large extent upon the severity of the conditions to which the grease is subjected, as well as the particular diaryl amine used. Generally, however, the amount of the diaryl amine employed is between about 0.1 and 1.5 per cent, by weight based upon the weight of the total composition. 7

;In preparing the compositions of the present invention, various methods may be used in compounding. and blending the lubricating oil with the other specified ingredients. The lithium soap may be prepared and then added to theoil, or the soap may be prepared in situ. According to one embodiment, when starting with commercially- It can be seen from the data in Table 1 that the addition of 0.125 to 1.0 part by weight of hydrogenated rosin results in consistency degradation. In view of this deleterious effect that hydrogenated rosin has upon lithium-base greases prepared from an oilxhaving a viscosity of about 500 SUS at it was indeed surprising to find the beneficial efiect the hydrogenated rosin has upon the consistency of greases prepared from the more viscous oils.

The improved consistency characteristics of the lithium-base grease compositions of the present invention as compared with similar lithiumbase greases containing either no rosin or "wood rosin in lieu of hydrogenated rosin are illustrated in Table 2. In these compositionsf one was a blend of mineral oils of the type normally used in making chassis lubricants. Oil B had a-vis 'cosity- 012700 SUS at 100 n. and 156 TABLE 2 Composition VII VIII IX X XI XII XIII Parts by Weight: I

Oil B 93.4 93.4 93.4 93 5 93.5 93 5 93 5 Lithium Stearate. 6. 6 6. 6 6. 6 Lithlum soap of the hydrogenated fish oil fatty acids 6. 5 6.5 6.5 6 6 Hydrogenated Rosin 0. 25 0.5 1. 1 Wood Rosin 0. Consistency (ASTM D21747T) Unworked 305 332 350 315 255 304 Worked 414 324 431' 405 343 275 335 Texture Grainy Smooth Smooth Grainy Smooth Smooth Smooth As can be noted from the data in Table 2, composition VII consisting of 93.4 parts by Weight of oil B and 6.6 parts by weight of lithium stearate had a grainy texture and un'worke'd and worked consistencies of 367 and 414, respectively." When only 0.25 part by weight of hydrogenated rosin was added to composition VII, a smooth grease" of improved consistency, as shown by composition VIII, was obtained. It will be noted from composition IX that wood rosin improved the texture of composition VII but that it was not as effective as hydrogenated rosin in improving the consistency of the grease. In fact, the wood rosin had a deleterious effect upon the worked consistency of the grease by increasing the pene tration to 431 in contrast to hydrogenated rosin which improved the worked consistency of the grease by decreasing the penetration to 324. By comparing composition X with compositions XI, XII and XIII, it will be noted that a grainy-textured grease consisting of 93.5 parts by weight of oil B and 6.5 parts by weight of the lithium soap of the hydrogenated fish oil fatty acids can be improved with respect to texture and also with respect to consistency by the addition of 0.5 to 1.5 parts by weight of hydrogenated rosin. Although the consistency of composition XIII, where 1.5 parts by weight of hydrogenated rosin were added, was about the same as the consistency of composition XI where only 0.5 part by weight of hydrogenated rosin was added; it nevertheless has improved consistency characteristics over composition 'X where no hydrogenated rosin was employed. -Of the greases prepared from the lithium soap of the hydrogenated fish oil fatty acids, composition XII wherein the ratio TABLE 3 Composition .1 XIV I I XV XVI Parts by Weight:

\ Oil C -l 93.5 3. 5 Q8. 5

Lithium scan of the hydrogenated fish oil fatty acids. 6. 5 6.5 6. 5 Hydrogenated Rosin 0. 5 1.0 Consistency (ASTM D2l7-47'I):

Unworked 344 272 305 Worked 403 314 335 Texture Smooth Grainy Smooth It can be seen from the data in Table 3 that the addition of 0.5 and 1.0 part by weight of hydrogenated rosin to composition XIV improved not.

only the consistency but also the texture of the composition. While the consistency of composi-- tion XVI was greatly improved over the consistency of composition XIV, composition XV wherein the ratio of hydrogenated rosin to lithium soap is 1 to 13 shows optimum improvement.

The use of hydrogenated rosin in the compositions of the present invention is particularly advantageous in that it produces a smoothtextured grease of improved consistency, reduces the bleeding tendency of the grease and decreases the amount of lithium soap required to produce a grease of a given consistency.

The properties'of a typical wheel bearing lubricant made in accordance with my invention are shown by the inspection data given in Table 4. The oil used in preparing this wheel bearing lubricant was a mineral oil blend having a viscosity of 1050 SUS at F. and 83 SUS at 210 F.

TABLE 4 Composition, per cent by weight:

Mineral oil. 91.6 Lithium soap of the hydrogenated fish oil fatty acids 7.3 Hydrogenated rosin 1.1

Inspection data Consistency (ASTM D217-47T) Unworked 256 Worked 280 Dropping point, F. (ASTM D56642) 364 Water resistance-rotating rack, water sprayed on panels at rate of 500 cc./minute for 15 minutes: i 1

Wheel hearing test data- U. S. Army spec.

AXS-1574, 220 F.-450 R. P. M.-6 hrs:

Flow of grease from hub None Grease on spindle None Leakage None Structure or consistency change Not apparent Deposits on bearings None MMM It is apparent from the data in the above table that the compositions of my invention are characterized by having good consistency values, a relatively high dropping point, gOOd resistance to leaching by water, excellent metal adhesion properties, low oil separation and good performance characteristics, as evidenced by the dat for the wheel bearing test.

The metal adhesion test referred to in the above table was carried out by filling a tared 1% inch concave disc (center depressed 3%) with the lubricant and spinning it at 1800 R. P. M. for seven minutes, after which the disc was weighed and the difference in weight calculated as per cent loss.

The oil separation test was carried out by filling a 1 inch nickel filter cone with the lubricant and placing the cone in a tared beaker. The beaker and cone were placed in an oven maintained at a temperature of 212 F. for 24 hours,-'after which the beaker was weighed and the gain in weight calculated as per cent oil separation.

While the invention has been described herein with particular reference to certain specific embodiments thereof by way of illustration, it is to be understood that the invention is not ,limited to such embodiments except'as hereinafter defined in the appended claims.

I claim:

.1. A smooth-textured lithium-base grease composition comprising essentially a homogeneous mixture of a mineral oil having a viscosity within the range of about 750 to about 4000 SUS at 100 F., a lithium soap in an amount sufficient to thicken the oil to the consistency of a grease and a hydrogenated rosin of at least about 40 per cent saturation, the weight ratio of said hydrogenated rosin to said lithium soap being between about 1:4 and about 1:30.

2. A smooth-textured lithium-base grease composition comprising essentially a homogeneous mixture of a mineral oil having a viscosity within the range of about 750 to about 4000 SUS at 100 F., 5 to per cent by weight of a lithium soap, and a hydrogenated rosin of at least about 40 per cent saturation, the weight ratio of said hydrogenated rosin to said lithium soap being between about 1:4 and about 1:30.

1 3, A smooth-textured lithium-base grease coma position comprising essentially a homogeneous mixture of a mineral oil having a viscosity within the range of about 750 to about 4000 SUS at 100 F., 5 to 15 per cent by weight of a lithium soap, and 0.2 to 1.5 per cent by weight of a hydrogenated rosin of at least about 40 per cent saturation.

4. A smooth-textured lithium-base grease. composition comprising essentially a homogeneous mixture of a mineral oil having a viscosity within the range of about 750 to about 4000 SUS at 100 F., 5 to 15 per cent by weight of a lithium soap,

and 0.2 to 1.5 per cent by weight of a hydrogenated rosin of at least about 40 per cent saturation, the weight ratio of said hydrogenated rosin to said lithium soap being between. about 1:4 and about 1:30.

5. A smooth-textured lithium-base grease composition comprising essentially a homogeneous mixture of a mineral oil having a viscosity within the range of about 750 to about 4000 SUS at F., 5 to 15 per cent by weight of lithium stearate, and 0.2 to 1.5 per cent by weight of a hydrogenated rosin of at least about 40 per cent saturation, the weight ratio of said hydrogenated rosin to said lithium stearate being between about 1: 4 and about 1:30.

6. A smooth-textured lithium-base grease composition comprising essentially a homogeneous mixture of a mineral oil having a viscosity within the range of about 750 to about 4000 SUS at 100 F., 5 to 15 per cent by weight of the lithium soap of the hydrogenated fish oil fatty acids, and 0.2 to 1.5 per cent by weight of a hydrogenated rosin of at least about 40 per cent saturation, the weight ratio of said hydrogenated rosin to said lithium soap of the hydrogenated fish oil fatty acids being between about 1: 4 and about 1:30.

7. An improved lubricant comprising essentially a homogeneous mixture of a'mineral oil having a viscosity within the range of about 1000 to about 3000 SUS at 100 F., 5 to 15 per centby weight of a lithium soap, and 0.2 to 1.5 per cent by weight of a hydrogenated rosin of at least about 40 per cent saturation, the weight ratio of said hydrogenated rosin to said lithium soap being between about 1:5 and about 1:20.

8. An improved chassis lubricant comprising essentially a homogeneous mixture of a mineral oil having a viscosity within the range of about 1000 to about 2000 SUS at 100 F., 5 to 15 per cent by weight of a lithium soap, and 0.2 to 1.5 per cent by weight of a hydrogenated rosin of at least about 40 per cent saturation, the weight ratio of said hydrogenated rosin to said lithium soap being between about 1:10 and about 1:20.

9. An improved chassis lubricant comprising essentially a homogeneous mixture of a mineral oil having a viscosity within the range of about 2000 to about 3000 SUS at 100 F., 5 to 15 per cent by weight of a lithium soap, and 0.2 to 1.5 per cent by weight of a hydrogenated rosin of at least about 40 per cent saturation, the weight ratio of said hydrogenated rosin to said lithium soap being between about 1:5 and about 1:10.

10. An improved wheel bearing lubricant com prising essentially a homogeneous mixture of a mineral oil having a viscosity of about 1000 SUS at 100 F., 5 to 15 per cent by weight of a lithium soap, and 0.2 to 1.5 per cent by weight of a hydrogenated rosin of at least about 40 per cent saturation, the weight ratio of said hydrogenated rosin to said lithium soap being between about 1:6 and about 1:20.

PAUL .R. MCCARTHY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 2,505,222 Weitkamp Apr. 25, 1950 

1. A SMOOTH-TEXTURED LITHIUM-BASE GREASE COMPOSITION COMPRISING ESSENTIALLY A HOMOGENEOUS MIXTURE OF A MINERAL OIL HAVING A VISCOSITY WITHIN THE RANGE OF ABOUT 750 TO ABOUT 4000 SUS AT 100* F., A LITHIUM SOAP IN AN AMOUNT SUFFICIENT TO THICKEN THE OIL TO THE CONSISTENCY OF A GREASE AND A HYDROGENATED ROSIN OF AT LEAST ABOUT 40 PER CENT SATURATION, THE WEIGHT RATIO OF SAID HYDROGENATED ROSIN TO SAID LITHIUM SOAP BEING BETWEEN ABOUT 1:4 AND ABOUT 1:30. 